Among internal combustion engines disposed in vehicles and the like, there is one type of engine in which an air suction system is provided by way of a countermeasure to cope with problems such as fuel consumption rates and harmful exhaust components. This air suction system is designed to achieve improvements in combustibility by imparting swirl to air that enters a combustion chamber or a cylinder.
Some of the above air suction systems are constructed in such a manner that an air intake port of an internal combustion engine is partitioned by a partition wall into first and second intake port sections. These two intake port sections separately open into a single combustion chamber of the internal combustion engine. The second intake port section has an air intake control valve positioned therein. This control valve selectively provides opening and closing actions depending upon an engine-running state. The partition wall has first and second injection passage portions defined therein. One ends of the first and second injection passage portions are brought together at a convergence portion. The other ends of the same two injection passage portions respectively lead into the first and second intake port sections on a downstream side of the air intake control valve. The other ends of the first and second injection passage portions are directed toward the combustion chamber. The partition wall is provided with a fuel injection valve which has first and second nozzle hole portions oriented toward the combustion chamber respectively through the first and second injection passage portions.
Such air suction systems for the internal combustion engines are disclosed in published Japanese Patent Application Laid-Open No. 4-262063, Japanese Utility Model Application Laid-Open No. 61-147336, and Japanese Utility Model Application Laid-Open No. 4-47165.
An air suction system taught by Publication No. 4-262063 is intended for use in an internal combustion engine in which a swirl port and a straight port is provided, both of which communicate with a single combustion chamber. The straight port is provided with an air intake control valve which provides a closing action under predetermined engine load conditions. Further, a partition wall for separating these two ports is provided with a communication passage on a downstream side of the air intake control valve. The communication passage intercommunicates the swirl port and the straight port. In addition, a fuel injection valve having two nozzle holes is disposed in the communication passage. The air suction system is characterized in that the partition wall is formed with projections on a wall surface thereof on the swirl port side. The projections are located on a downstream side of the communication passage. The projections produce the breakdown of a flow of intake air over the wall surface.
According to another air intake system shown in aforementioned Publication No. 61-147336, first and second air intake ports communicate with a combustion chamber via air intake valves. The first intake port is helically shaped, while the second intake port is straightly shaped. The second intake port is provided with an air intake control valve. This control valve is closed at low speed and light load regimes of an internal combustion engine. A fuel injection valve having two nozzle holes is mounted in such a manner that the nozzle holes are respectively opened into the first and second ports by a partition wall at a location between the air intake control valve and the air intake valve. The partition wall separates the first intake port from the second intake port.
According to yet another air intake system carried by the aforesaid Publication No. 4-47165, first and second air intake ports communicate with a single cylinder. The second intake port has an air intake control valve positioned therein. This control valve selectively provides opening and closing actions in response to an engine-running state. A partition wall for separating these two ports is provided with first and second injector ports. A fuel injection valve having two nozzle holes is disposed at a location where the first and second injector ports are joined together. An upper edge of the partition wall is position in a downstream direction from upstream ends of openings of the first and second injector ports, the openings leading into the first and second intake ports.
In conventional air suction systems, there is an inconvenience in that a swirl ratio during air suction decreases with an increase in the area of each passage cross-section of first and second injection passage portions. These two injection passage portions are communication apertures which intercommunicate first and second air intake port sections.
Another inconvenience occurs when the aforesaid communication apertures, or rather the first and second injection passage portions, are formed in such a manner that the respective passage cross-sections thereof are reduced in area in order to overcome the aforesaid problem. That is, an insufficient air current flows into the second intake port section when the air intake control valve is closed. As a result, fuel adheres to an inner wall surface that forms the second intake port section.
A further inconvenience arises when fuel is ejected through the aforesaid first and second injection passage sections. That is, the air current, which flows through the first and second injection passage portions, blocks fuel from being injected into the first intake port section.
To obviate the aforesaid inconveniences, the present invention provides an air suction system for an internal combustion engine in which an air intake port of the internal combustion engine is partitioned by a partition wall into first and second intake port sections which separately communicate with a single combustion chamber of the internal combustion engine, the second intake port section being provided with an air intake control valve which selectively provides opening and closing actions depending on an engine-running state, the partition wall being defined with first and second injection passage portions whose one ends are joined together at a location of the partition wall, the other ends of the first and second injection passage portions being respectively in communication with the first and second intake port sections on a downstream side of the air intake control valve, the other ends of the first and second injection passage portions being oriented toward the combustion chamber, the partition wall being provided with a fuel injection valve which has first and second nozzle hole portions directed toward the combustion chamber respectively through the first and second injection passage portions;
the improvement according to a first embodiment wherein a passage cross-section of the first injection passage portion is established to be greater in area than that of the second injection passage portion;
the improvement according to a second embodiment wherein the first and second injection passage portions are configured in such a manner that respective passage cross-sections thereof adjacent to the first and second nozzle hole portions have an area equal to a predetermined smaller cross-sectional area, and wherein the first and second injection passage portions are configured such that respective passage cross-sections thereof on the sides of the first and second intake port sections have an area equal to a predetermined larger cross-sectional area, the predetermined larger cross-sectional area being greater than the predetermined smaller cross-sectional area; and
the improvement according to a further embodiment wherein the first and second injection passages are formed with taper-shaped configurations such that the area of each passage cross-section increases in stages in the direction of the first and second intake ports away from the side of the air intake control valve.
According to the first embodiment of the invention having the above structure, some of an air current flowing in the first intake port section is led into the second intake port section through the first and second injection passage portions when the air intake control valve is closed. This stream of airflow eliminates the likelihood that fuel resides and adhere to respective inner wall surfaces of the second injection passage portion and the second intake port section. In addition, the passage cross-section of the first intake port section is established to be greater in area than that of the second injection passage portion. The first and second injection passage portions respectively communicate with the first and second intake port sections. As a result, although some of the airflow in the first intake port section is brought into the second intake port section, fuel is injected into the first intake port section without being interrupted by the aforesaid partial airflow.
When the air intake control valve is opened, fuel from the fuel injection valve is supplied to the first and second intake port sections respectively through the first and second injection passage portions. The supplied fuel is then smoothly introduced into the combustion chamber, together with respective airflows in the first and second intake port sections.
According to the second embodiment of the invention having the above structure, the first and second injection passage portions are configured in such a manner that respective passage cross-sections thereof adjacent to the first and second nozzle hole portions of the fuel injection valve have an area equal to a predetermined smaller cross-sectional area. This arrangement can ensure a proper stream flow of air from the first intake port section to the second intake port section to avoid reducing a swirl ratio during air suction. Further, the first and second injection passage portions are formed in such a manner that respective passage cross-sections thereof on the sides of the first and second intake port sections have an area equal to a predetermined larger cross-sectional area which is greater than the aforesaid predetermined smaller cross-sectional area. This configuration enables ejection of fuel in a wider range of injection without allowing the fuel to contact respective wall surfaces of the first and second injection passage portions.